Queuing for a game
The best game mode to queue for if you are new to the game is All Pick. This will allow you to choose a specific hero you want to play that you enjoy, or just randomly pick heroes to help you get used to all of the different heroes. As far as queueing for a server, simply pick the servers closest to you, in order to reduce the lag you will experience in game. The only time you should disregard this is if you are Russian or Brazilian, in which case make sure to queue for all servers.
Picking a hero
There are many types of heroes in Dota, but they all fall into two main categories: carries and supports. The job of a carry is to 'carry' your team to victory, to accumulate gold through killing creeps, get strong items and kill the enemy team. The job of a support is to 'support' the carry to do this. As the goal of Dota is to kill the enemy heroes in order to push and win, you can see that carries are by far the stronger heroes in the game. The rule is:
A good carry does not need supports on his team to play well. Supports are a crutch for bad players
Always pick a carry if you want to benefit your team. As many players still labour under the delusion that picking supports is beneficial, or that you should not have too many carries on one team, make sure you pick your hero as late as possible. This will make it more likely that your team mates pick carries instead of supports, as they see less carries on their team.
Starting the game
As you start the game, you will have to buy your starting items and choose which lane you want to go to. There are several main rules to this.
1. It is never your job to buy a courier. A courier is essential for your team to do well, but you need items to do well, and you need them more than your teammates do.
2. Calling a lane first means nothing, it's who gets there first. Many players will 'call' a lane they want to play in. If you are not fast enough, and someone else calls your chosen lane, simply walk into the lane before them. If they point out that they called the lane, acceptable responses are to deny this or say nothing. Make sure you do not leave even if they try and displace you in the lane. In rare situations they will come into the lane anyway and stay there. This is referred to in competitive play as a TRILANE
General gameplay tips
The following is a list of some useful gameplay tips and things to keep an eye out for while playing the game.
1. It is never your job to buy wards. Same reasoning as for the courier.
2. Any miss call is a late miss call if you die. A miss call is when a player calls that one of the heroes they have been laning against has left the lane. This can indicate that they are going to another lane for a gank. If you are ganked in your lane by a hero from another lane and die from the gank, then it is the fault of the person whose lane they came from not your own. If the miss call had been early enough clearly you would have lived.
3. Always autoattack the creeps. You get money for last-hitting creeps. You are more likely to get the last hit if you hit a creep more. Simple.
4. You always need last hits more than your lane partner
5. It is not your job to initiate. You are the most important person on your team. If you initiate, you die first. You can't fight if you're dead.
6. Farm while your team push. If your team is pushing, or engaging the enemy team, this is the perfect opportunity for you to farm unmolested. Take the time and use it well.
And finally the golden rule: Nothing is ever your fault
If you die, your allies did not call miss at all, early enough, or help you enough during the fight. If your allies die, it is because they misplayed, not because you didn't help them enough. Make sure you do not let your allies get away with these mistakes.
Harnessing your inner asshole: in-game communication in Dota 2
Communication is essential in a team game. Here are some ways that you can better communicate with your teammates in order to lead your team to victory.
1. Ping the map if you want your allies to do something. If they do not at first respond, ping more insistently, making sure to alternate between pinging on them and the map. Do not explain in chat what you want, pinging should always be clear enough.
2. Encourage your teammates who are not doing well to improve by flaming them in team chat. Acceptable ways to flame players who mess up are: "This [insert hero name here]", "First game [insert hero name here]?", 'Uninstall Dota 2 please", or the classic "gg, noob [insert hero name here]". If they do not start doing well, then you need to repeat these sentiments in all-chat.
3. Shame players for their cowardice. If you see a player running away from a teamfight after it has been lost, or worse a player who is on the other side of the map and not in the fight, make sure to ping continuously on their position on the minimap, so everyone can see what a coward they are.
4. Do not tolerate criticism. Even if you have a bad K/D it is because your teammates stole your kills and let you die. If any player on your team or the other team flames you, make sure to respond with 'stfu noob'. This will stop them from criticising you any further, and will make them realise that you know best.
5. Make sure the other team knows it is your teammates fault when you lose. This will make your teammates question their play and help them improve, as they will not want to be shamed in front of an opposing team again.
6. Report players who feed, whether intentionally or not. Would you wan to play with a feeder again? Would anyone else? I didn't think so.
7. Do not give a reason when you pause the game. It does not matter why you have to pause or how long for, Dota is a 5v5 game and should only be played as such. Everyone should wait for you.
8. Always ask for a commendation at the end of every game. You've earned it.
I can't pretend that this guide is remotely comprehensive, but I hope that at least some of the tips contained here will help some people to get the most out of their Dota 2 pub experience.